A Human-Ocean Health Index (HOHI) for integrated assessment under the cumulative effects of human activities and...

An integrated assessment of the human-ocean coupled system is urgently needed for sustainable coastal management. This study introduces the Human-Ocean Health Index (HOHI) framework, which is a novel composite index that extends the Ocean Health Index (OHI) framework by integrating three interactive dimensions (sea use coordination, water cumulative effects, and ecosystem services) to evaluate the system health, using the bibliometric analysis method to determine the weights of each dimension, and applying it to Xiamen Bay, China, under four climate and management scenarios. Results indicate that (1) the baseline HOHI (0.751) classifies Xiamen Bay as healthy, with 44% of subzones in a sub-healthy state, particularly in industrial areas, (2) spatially, HOHI was most strongly associated with ecosystem services, though this correlation does not imply causation, (3) climate change alone reduced HOHI (-2.40%), whereas restoration management increased it (+1.5%), confirming the potential of interventions to mitigate impacts. Crucially, further expanded restoration led to a net decline in HOHI (-0.81%) due to exacerbated sea-use conflicts, revealing a critical spatial trade-off. (4) The HOHI demonstrated high analytical robustness: bootstrapping revealed minimal inherent uncertainty (coefficient of variation <0.11%, 95%CI width < 0.03), and a sensitivity analysis confirmed that core findings on scenarios ranking were independent of the weighting method. These findings offer an evidence-based diagnostic tool for evaluating the potential implications of marine spatial planning and ecosystem health assessment.